Various microwave devices such as resonators, delay lines, filters, antennae and distribution networks for antennae utilize components which are coated with uniform films prepared by laser ablation. Active electronic devices such as flux flow and SNS devices, as well as passive electronic devices such as impedance matching transformers, also use uniform films prepared by laser ablation. The components being coated may be of any material with magnesium oxide and lanthanum aluminate being preferred.
The material ablated by the laser to prepare the uniform film may be selected from a number of materials, but the primary material used is yttrium barium cuprate (YBa.sub.2 Cu.sub.3 O.sub.7-.DELTA.). In accordance with prior art procedures and as illustrated in FIG. 1, a flat disk of this target material or other target material is impinged upon by an eximer laser beam. The laser beam causes particles of the 10 material to erode from the target and be ejected into cones within a solid angle of about 5.degree. having a centroid normal to the surface of the irradiated portion of the target. Therefore, the area on the substrate being coated can only be slightly larger than the irradiated target area. Accordingly, because target materials are typically only provided as disks which are smaller than the device or component that is to be coated, it is necessary to shift the target or substrate laterally with respect to one another in order to coat the desired area. As those skilled in the art recognize, this complicates the processing of substrates and leads to situations in which the film coating the substrates is not uniform due to film overlap.
In view of the aforementioned shortcomings in utilizing a target with a flat target area, there is a need for an approach to coat larger areas of substrates utilizing targets of conventional or readily available diameters.